Work performance breathing normoxic nitrogen or helium gas mixtures

Abstract

Twelve subjects completed a progressive treadmill test to maximal aerobic capacity while breathing air or a 79% helium--21% oxygen gas mixture (HeO2). Metabolic and thermoregulatory responses to work while breathing the two mixtures were compared at rest, 30-40%, 60-70%, and 85-90% of maximal performance, and at maximal effort. Ventilation, ventilatory equivalent, and respiratory rates were increased and oxygen uptakes decreased by breathing HeO2 when the level of work exceeded 85-90% of maximum. Heat loss through the respiratory tract was greater breathing HeO2. The reduction in maximal oxygen uptake is probably due to a reduction in the oxygen cost of breathing a less dense gas. It was not related to a lower body temperature and probably not to O2 transport or circulatory limitation. HeO2 breathing had no effect on maximal mechanical work capacity.

The Effects of Breathing He–O2 Mixtures on Maximal Oxygen Consumption in Normoxic and Hypoxic Men

“…less than expected on a merely physical basis. These findings in normoxia are in good agreement with previous reports at maximal exercise (Wilson & Welch, 1980;Brice & Welch, 1983), although other investigators (Spitler et al 1980) observed a lower increase in ýE during He-Oµ breathing. Three factors may explain this apparent discrepancy.…”

“…In fact in the horse, He-Oµ breathing had no effect on ýOµ,max in normoxia (Erickson et al 1994), but increased (Erickson et al 1995) ýOµ,max in hypoxia . As far as humans are concerned, He-Oµ breathing has been reported to increase (Robertson & McRae, 1966;Brice & Welch, 1983), decrease (Murphy, Clark, Buckingham & Young, 1969;Spitler, Horvath, Kobayashi & Wagner, 1980) or have no effects (Bowers & Fox, 1967) on ýOµ,max in normoxia. No previous studies, to our knowledge, have investigated the effects of He-Oµ breathing on ýOµ,max in humans exposed to acute hypoxia.…”

Effects of Loading and Unloading the Respiratory System on Respiratory Control and Muscle Function

“…Breathing gas of decreased density, by de creasing respiratory impedance, has the opposite effect on lung mechanics and ventilatory behavior [3,15,16], Utilizing different gas densities to study hyperoxic hypercapnia, the SF6 mixture was more than three times denser than that of the control (N2) gas, while the He mix ture was half as dense (table 1). The viscos ity of the three mixtures were comparable so that density was the independant var iable for the gases.…”

“…In previously reported studies with He, pleural pressure or Pdj and P01 were measured during exer cise and occlusion pressure was measured during room air breathing [16,23,24]. In these studies, pressure generation de creased while ventilation increased or re mained unchanged.…”

Heliox, dyspnoea and exercise in COPD

“…Initial sporadic experimentation investigated physiological responses to Heliox [12,13] but, since the late 1980s, an increased global focus on reducing asthmatic morbidity and mortality reinvigorated the prior enthusiasm associated with Heliox [14]. During the late 1990s, randomised controlled trials concentrated on the potential benefits Heliox may provide as an adjunct therapy to aid noninvasive ventilation and reduce intubation rates during acute exacerbations of COPD [15][16][17][18].…”